Heater



May 8, 1934. B. E. MaCDoUGALL HEATER Filed Oct. 17. 1932 Patented May 8, 1934 UNITED STATES HEATER Bruce E. MacDougall, Toronto, Ontario, Canada Application October' 17, 1932, Serial No. 638,049

4 Claims.

'This invention relates to heaters and more particularly to the type in which a fan is used in conjunction with an electric heating element and my object is to devise an eicient heater oi this character which will produce a large volume of heated air having a high temperature with a minimum consumption of electric energy.

The principal features of the invention consist in the novel construction and arrangement of a ian within an encircling casing directing a new of air through a grid of refractory material supporting an electric heating element on the side remote rorn the ian, the grid being provided with a plurality of converging air passages therethrough presenting an extraordinary area of heating surface and effecting' the exposure of the air passing therethrough to the maximum effect of the direct heat rays produced by the electric element.

The construction and functions of the various elements are hereinafter more fully described and are illustrated in the accompanying drawing in which:

Fig. 1 is a. longitudinal section of my heater;

Fig. 2 a cross section on the line 2 2 in Fig. l; and

Fig. 3 a side elevation of a modified shape of heating element.

In the drawing like numerals of reference indicate corresponding parts in the different fig.- ures.

1 is an open ended casing, which in the portable type of heater as shown, is preferably cylindrical and formed of sheet metal in two parts la, lb each being curved inwardly to forni converging iianges c and b. These parts may be .secured together by interlocking ribs 1C, ld formed :on the peripheries of the parts and plates 2 are `secured thereto on the outer side at diametrically opposite points. These plates also serve to carry trunnions which are journalled in the ends of a fork 3a forming part of a stand or pedestal 3. .Any suitable clamping means, such as nuts 4 `threaded on the outer ends of the trunnions for frictional engagement with the forked ends 3a, may be employed to retain the casing as adjusted in desirably adjusted position.

A grid 5 preferably formed of a refractory material such as porcelain having its external di ameter smaller than the internal diameter of the casing i is supported therein by lugs 6 leaving an annular air passage 7 around the grid. The grid here shown'is formed with a plurality of concentric Webs 5 which are spaced apart by the openings 5b. The Webs 5a are connected (Ci. 21g-39) together by radially arranged ribs 5c which are so spaced apart circumferentially of the grid that the openings 5b are of maximum length Without unduly weakening the structure. The front faces of the Webs are formed with grooves C@ .5d to receive the heater elements 8 formed of resistance wiring. It will be noted that the Webs are V shaped in cross section and the passages formed therebetween have convergent walls 5e which present an extraordinary area for Contact with the air passing through the grid.

A ian 9 located at the rear side of the grid 5, remote from the resistance wiring 8 is carried on a spider l0 which is suitably supported on the rear part 1b of the casing 1. The blades of the 7o fan are adapted to create and direct a current ci air through the air passages 5D and 7 and through additional openings 5 formed in the central portion 5S of the grid adjacent the innermost web 5e. The central portion 5g thus forms 75 means for preventing the passage of air through the center of the baille-support 5 so that current of air from the fan is forced through the passages 5b, 5f and 7.

It Will be readily understood that the refractory material of the grid absorbs a considerable quantity of heat from the heating element arranged in the grooves in the front face thereof and quickly attains a high temperature. The current of air directed toward the grid by the fan impinges 35 Aupon the convergent surfaces of the passages through the grid and a considerable heat eX- change occurs which is inagniiied by the fact that the pressure exerted by the fan forces the air through these convergent passages. The slight compression of the air efiected by the fan pressure, in addition to the heat imparted thereto causes the lair to expand upon emerging from the restricted areas of the passages through the grid and to circulate in eddy currents immediately over the embedded heating elements so that the maximum absorption of heat is absorbed from the direct heat rays emanating from such elements.

The air flowing around the outer wall of the grid impinges upon the inwardly curved iiange a of the casing and is directed inwardly toward the centre and causes the column of air to be projected well beyond the casing before it spreads to dissipate its heat.

A grill 11 is carried in any suitable manner on the open end of the casing l at the front end thereof and in front of the resistance wiring 8. This grill not only serves as a protective device for the Wiring but as a support for a cooking 110 vessel when the casing is swung on its trunnions to position the grill horizontally. The rear end of the casing may be provided with a screen 12 to exclude dust and dirt.

A device such as described is extremely eiiicient in effecting the exchange of heat units produced by the electric current to a current of air passed therethrough and while a particular arrangement of air passages through the grid are shown and described it will be understood that these may be varied considerably while retaining the principal features of the protected element and the coverging heating walls.

In Fig. 3 a modiiied shape of baffle-support 15 is shown in which the resistance wiring 8 is strung on webs l5fb extending across the grid. 1n this case the openings 15b are formed on opposite sides of a plurality of the convolutions 8a of the wiring 8. The terni convolution is intended to mean any stretch of resistance wiring.

Any suitable means may be employed to connect the wiring 8 and fan 9 with a source of electric energy and to control them in any desired manner.

What I claim as my invention is:

l. A heater comprising a casing, a grid having air passages therethrough converging in a forward direction, a fan directing a ilow cf air forwardly against the converging walls of said grid, and a heating element arranged on said grid between the passages therethrough on the side thereof opposite to the fan, whereby the forward air flow from said fan impinges against the converging walls of the air passages in extensive heat exchange contact.

2. A heater comprising a casing, a grid of refractory material, a heating element supported on one side of said grid, a fan arranged in said casing directing a current of air against said grid on the side opposite to said heating element, and air passages through said grid spaced between said heating element and having wall surfaces diverging rearwardly from the heating element toward the fan whereby they Contact angularly with the air ow therefrom.

3. A heater comprising a casing, a grid of refractory material supported in said casing and formed of a plurality of Webs of V-shaped cross section forming converging air passages, an electric heating element arranged on the broad faces of the webs extending between the convergent walls, and a fan directing a current of air through said passages from the flaring sides.

4. A heater comprising a circular grid of refractory material presenting a series of narrow spaced webs having grooves formed in one face thereof, an electric heating element embedded in said grooves and directing heat rearwardly into said webs and forwardly therefrom, said webs being tapered rearwardly to present extended heat exchange surfaces and forming a plurality of air passages of forwardly converging form on either side of said embedded elements, and a fan projecting a column of air forwardiy against the converging heating faces of said webs.

BRUCE E. MACDOUGALL. 

